Field of the Invention
This invention relates to underwater measurements, and particularly to pipeline inspection using an autonomous underwater vehicle (AUV) for monitoring of ground, underground, and subsea structures and facilitating inspection or other operations performed on or near the structures. The invention further relates to surveying the condition of ground, underwater and underground structures for maintenance scheduling on said structures.
Background of the Invention
The major causes of pipeline failures around the world are external interference, and defects in metal such as corrosion and cracks—in combination with the stress they experience; therefore, assessment methods are needed to determine the severity of such defects (taking into account the mechanical stress) when they are detected in pipelines. Pipeline integrity management is the general term given to all efforts (design, construction, operation, maintenance, etc.) directed towards ensuring continuing pipeline integrity.
When carrying out an inspection, all prior art autonomous underwater vehicles (AUVs) must be designed to follow an appropriate subsea structure within a close proximity in order to provide useful and accurate information. Typically, At/Vs carry various types of equipment to form images of a surveyed underwater structure. Such equipment typically implements either a sonar technology or visual imaging. MA's can normally follow the structure autonomously, without any needed help from an external operator.
The prior art primarily consists of surveying and inspection facilities limited to inspection operations on pipeline metallic surfaces by inspection means external to the underwater pipeline. It is limited to detection of an obvious bole m the pipe leading to the product (oil or gas) leakage or detection of the free sagging. If the defect is not a through-hole or if the pipeline is placed under ground, an additional means are required to identify the defect.
The present invention addresses prior art problems including, but not limited to, (1) sensor positioning, (2) AUV operation control, during, underwater pipeline inspection, and (3) inspections performed directly inside the pipeline either underwater pipeline, underground or the pipeline at the surface.